With the tremendous and rapid development in the field of scientific technology, various portable electronic devices nowadays, covering such as mobile devices, smart devices, wearable devices and so forth, have continuously innovated and advanced, in order to draw people's attention as much as possible. In all of these devices, to have a fundamental function of lightening is necessary for usages of indication, illumination or lightening. Accordingly, since a backlight module (BLM) has multiple advantages including having a thin and slim thickness and being capable of generating a surface light, it starts to be extensively adopted in these devices.
As if it is classified merely concerning about the target the BLM illuminates, in the state of the art, the BLM can be approximately classified into two major types as follows: a typical white light BLM used for illuminating a display module, also referred to as a display-use BLM, and a typical mono-color light BLM or multi-color light BLM used for illuminating a non-display module, also referred to as a non-display-use BLM. For the display-use BLM, since the illuminated target the liquid crystal display module is equipped with multiple color filters, to emit a basic white color surface light is enough for this type of BLM. After cooperating with the multiple color filters in every pixels in the display module, the white light provided by the BLM is capable of rendering every pixels to generate different color of lights, whereby a collection of all pixels finally form a picture or an image.
As to the non-display-use BLM, for example, a keypad backlight module for illuminating a keypad module, which may be disposed on a keypad protective cover. In addition to provide a white color of light, it is usually required to emit more different color of lights to meet various complex requirements, such as a blue color of light, a red color of light or a green color of light. Usually the light such kind of BLM emits is required to have better performances on no matter senses of comfortable, gentle, fashionable and modern feelings. Thus the light sources in such kind of BLM can provide different color of lights to cause to the BLM to be capable of become a multi-color light BLM.
FIG. 1a is a schematic diagram illustrating a lateral cross-sectional structure for a display-use type BLM in the prior art. FIG. 1b is a schematic diagram illustrating a top-viewed structure for a display-use type BLM in the prior art. Inside a containing space in an upper case 18 in a conventional electronic device 100 such as a tablet computer, a smart phone or a laptop computer, it is equipped with a conventional BLM 10, which has a laminated structure consisting of a light source 11, a light guide film 12, a light mask film 13 and a reflecting film 14. The light source 11 is typically arranged in a position very close to an edge E of the upper case 18, and receives electric power provided from a flexible circuit board 15 to emit light. A LCD display 16 is assembled above the BLM 10.
The light mask film 13 includes a transparent part 131. The light 111 passing through the light guide film 12 and emitted from the light source 11 keeps passing through the transparent part 131 on the light mask film 13 and then emits out from a light output surface 17 to illuminate the LCD display 16. The BLM 10 and LCD display 15 are assembled inside the upper case 18. Since the target the BLM 10 illuminates is a LCD display, the BLM 10 is a white light BLM.
However, in the state of the art, no matter a display-use backlight module and a non-display-use backlight module, the modules simply provide a surface light source by collecting, concentrating and reflecting a light beam sourced from a light source to a specific surface, so as to form a surface light source at and emitted out of the specific surface. Such a backlight module can just provide a single surface light source and is primarily utilized to illuminate a display module or a keyboard or keypad module. That is the conventional backlight module is used as a light source to emit and provide a single surface backlight source only, but not used to provide or share a light to illuminate any lightening components else disposed in the electronic device 100, such as an indicating light or an indicator. Usually an additional light source module is demanded to be disposed in the electronic device 100 to provide a light source to illuminate the indicating components.
Nevertheless, by reviewing the structure of the BLM, it finds a technical feasibility, to redesign a back surface that is opposite to a typical light output surface on the BLM, to behave as another light output surface on the BLM, whereby the BLM can possibly have a second light output surface or a second surface light source, so as to illuminate a trademark logo on the rear case or behave as a light source to provide light to any indicating component on the device. The conventional BLM with outputting a single surface light source can be turned into a novel BLM with dual light output surfaces or dual surface light sources.